help to know if by "illegal" you're referring to Federal law, state laws or even municipal codes. Heck, it would even help to know if you're asking about the US, Canada, Mexico or Belgium for that matter....
Assuming that you're asking about the US, and further that
you mean Federal law, then no, there's no "black-letter" prohibition against fisting or (I think) peeing in a video.
Obscenity law is complex, and more than a little circular. (If it's found to be obscene, it's obscene, no matter what it is....)
Some state laws are so narrowly written that "touching a clothed or unclothed breast..." is obscene if the work it's in fails the Miller test, for example.
But maybe none of this pertains to the question you were really asking...
Scott Kinney
Diversified Video Associates
www.xxx-imports.com
[Link]